For now,
If you are only gaming, i5 is the wiser choice.
If you do more than just gaming, like streaming while gaming or video editing, etc., you might wanna consider the i7.
If you are having something else in mind like a gamble that future gaming will be able to use more threads, investing extra money to get an i7 is not bad.
Now, about k or non-k, if you have money, always get the k due to OCability. OC will prolong the usage life of your processor.
I would not compare i5 k with a non-k i7, since OC and extra threads can not really compared to each other.